1. Technical Field
The present invention relates generally to battery packs utilized in portable battery powered electronic devices, and, specifically, battery packs which monitor capacity and indicate pre-removal. Electronic devices may respond to such pre-removal indications to, for example, save operational state information prior to power loss.
2. Related Art
Portable electronic battery powered devices have made great advances in increased power and utility in furtherance of achieving reductions in costs and size and increases in portability. Applications of portable electronic devices such as portable data collection and processing terminals often require the operator to be mobile and roaming. As such, portable electronic devices are generally powered by a reusable, self-contained power supply. In particular, portable electronic devices are usually configured with rechargeable batteries, often disposed in some form of battery pack.
Quite often, an operator of a portable electronic device does not know the present state of charge of a battery pack, unknowingly setting off with insufficient battery resources to complete an extended task. In many circumstances, monitoring circuitry which determines the state of charge only exists in associated charging docks. However, if the charging dock is not readily available to the operator, partially and fully discharged battery packs are unfortunately often relied upon. Although monitoring circuitry may also exist within some portable electronic devices, the operator is still forced to install each battery pack into such portable electronic devices to determine the present charge. This process often proves tedious and time consuming, especially when multiple battery packs are needed to complete the task.
For example, when a portable electronic device does provide monitoring circuitry, the operator must: 1) open the battery compartment of the portable electronic device; 2) insert or replace the installed battery pack; 3) close the battery compartment; 4) evaluate the charge level from some type of user interface; and 5) repeat the entire process for each battery needed for a given task and for each battery that proves to be undercharged. To be safe, this process must be carried out each time the operator prepares to leave the vicinity of other available battery packs. Otherwise, the operator is forced to take along many additional battery packs that will typically not need to be used.
Additionally, it is well known that batteries are somewhat ohmic, and battery charge levels generally decreases linearly over time. Thus, the charge state of a battery can be determined by examination of the output voltage of the battery. Various methods of detecting when battery voltage rises or falls below a threshold level are also well known in the art. However, the various methods typically place an additional load on the battery to accomplish such detection. Similarly, displaying any information to an operator causes further battery loading.
As evidence that battery pack charge status via docking and insertion is an insufficient solution to their problems, operators have adopted and rely upon rudimentary, unreliable methods to attempt to determine charge status. For example, many operators short battery pack terminals together with a wet finger or tongue in order to judge the battery pack charge status by the imparted "shock." The use of saliva in such instances is unsanitary, unpleasant and may cause corrosion or otherwise result in resistively coating the battery pack terminals. Such rudimentary techniques are inherently unreliable, suffering from error in human judgment.
Moreover, if an operator removes a battery pack for any reason during the operation of the portable electronic device, the portable electronic device immediately loses its current state of operation including all data associated therewith. Such loss also occurs when a battery pack accidentally pops out of the slot, for example, when a portable electronic device is dropped. With most portable electronic devices, to avoid loss, the user must save, gracefully exit all application programs and turn off the portable electronic device before removing and replacing the battery. This entire process is very time consuming, annoying and unavailable upon accidental battery removal.
Thus, there lies a need for the operator of a portable battery powered electronic device to be able to readily determine the present state of charge of a battery pack. The operator needs to be able to readily compare the present state of charge of a battery pack to the states of charge of several rechargeable battery packs at once, and to be able to make quick, simple and accurate determinations of remaining battery capacity. Further, there lies a need for the operator to be able to exchange battery packs during use of portable electronic device without being burdened with a time consuming, preparatory shutdown process.